The following invention relates to a printhead assembly capping device for a printer.
More particularly, though not exclusively, the invention relates to a capping device for a printhead assembly of an A4 pagewidth drop on demand printer capable of printing up to 1600 dpi photographic quality at up to 160 pages per minute.
The overall design of a printer in which the capping can be utilized revolves around the use of replaceable printhead modules in an array approximately 8xc2xd inches (21 cm) long. An advantage of such a system is the ability to easily remove and replace any defective modules in a printhead array. This would eliminate having to scrap an entire printhead if only one chip is defective.
A printhead module in such a printer can be comprised of a xe2x80x9cMemjetxe2x80x9d chip, being a chip having mounted thereon a vast number of thermo-actuators in micro-mechanics and micro-electromechanical systems (MEMS). Such actuators might be those as disclosed in U.S. Pat. No. 6,044,646 to the present applicant, however, might be other MEMS print chips.
In a typical embodiment, eleven xe2x80x9cMemjetxe2x80x9d tiles can butt together in a metal channel to form a complete 8xc2xd inch printhead assembly.
The printhead, being the environment within which the capping device of the present invention is to be situated, might typically have six ink chambers and be capable of printing four color process (CMYK) as well as infra-red ink and fixative. An air pump would supply filtered air through a seventh chamber to the printhead, which could be used to keep foreign particles away from its ink nozzles.
Each printhead module receives ink via an elastomeric extrusion that transfers the ink. Typically, the printhead assembly is suitable for printing A4 paper without the need for scanning movement of the printhead across the paper width.
The printheads themselves are modular, so printhead arrays can be configured to form printheads of arbitrary width.
Additionally, a second printhead assembly can be mounted on the opposite side of a paper feed path to enable double-sided high speed printing.
It is an object of the present invention to provide a printhead assembly capping device.
Another object of the present invention is to provide a printhead assembly including a capping device providing an air flow path during operation of the printer and serving to prevent ingress of foreign particles to printhead nozzles during non-operational period of the printer.
The present invention provides a printhead assembly for a drop on demand ink jet printer, comprising:
a printhead module having a printhead including ink jet nozzles, the module being affixed to the assembly,
a capping device affixed to the assembly and movable linearly with respect thereto, the capping device at least partially surrounding the printhead module and movable between a capped position whereby the nozzles are capped by the capping device and an uncapped position whereby the nozzles are uncapped.
Preferably a plurality of printhead modules are situated along a channel, the modules and channel extending substantially across a pagewidth.
Preferably the capping device partly surrounds the channel.
Preferably the capping device has an onsert molded elastomeric pad which bears onto one or more of the printhead modules.
Preferably each printhead module includes a nozzle guard to protect the nozzles and wherein the elastomeric pad clamps against the nozzle guard in the capped position.
Preferably the elastomeric pad includes air ducts via which air is pumped to the printhead modules when the capping device is in the uncapped position.
Preferably a camshaft bears against the capping device and serves to move the capping device between said capped and uncapped positions.
Preferably the capping device includes a spring to bias the device with respect to the printhead modules against the camshaft.
Preferably the capping device is formed of stainless spring steel.
Preferably each printhead module includes a ramp and wherein the capping device includes a boss that rides over the ramp when the capping device is moved between the capped and uncapped positions, the ramp serving to elastically distort the capping device as it is moved between said capped and uncapped positions so as to prevent scraping of the device against the nozzle guard.
Preferably each printhead module has alternating air inlets and outlets cooperating with the elastomeric pad so as to be either sealed off or grouped into air inlet/outlet chambers depending on the position of the capping device, the chambers serving to duct air to the printhead when the capping device is uncapped.
Preferably the capping device applies a compressive force to each printhead module and an underside of the channel.
Preferably rotation of the camshaft is reversible.
As used herein, the term xe2x80x9cinkxe2x80x9d is intended to mean any fluid which flows through the printhead to be delivered to print media. The fluid may be one of many different colored inks, infra-red ink, a fixative or the like.